Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design and depicting a first embodiment of the graphical user interface; and,

FIG. 2 is a front view depicting a second embodiment of the graphical user interface.

The broken line showing of the display screen in FIGS. 1 and 2 illustrates environmental structure, and the broken line showing of additional icons in FIG. 1 illustrates unclaimed portions of the graphical user interface. The broken lines form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 